Technician1002 wrote:I gotta ask, What happened to the original piston?

Lost it in move! The valve portion was always unscrewed when not in use, so of course the piston was removed too. And it got lost...

Free to pick up. I live right next to Houston. Should be someone here I reckon. 5 million people...

Well, considering it was build completely from at least sch40, it could be for higher pressures if you wanted...I just have a general rule of no higher than 40-60psi for PVC, period. I do not care.
Sch40 does not indicate that the pipe is pressure rated. Most of the fittings on your cannon look ...

Well, considering it was build completely from at least sch40, it could be for higher pressures if you wanted...I just have a general rule of no higher than 40-60psi for PVC, period. I do not care.

http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html

Looking at the chart, 4" pvc ...

You might want to do some tests before you ship it out (if you can find a way to seal the barrel temporarily) and whoever receives it should also do some tests. I have PVC cannons that have been sitting in my garage for as long as five years and I am quite apprehensive about using them ever again ...

Nice try, no way in hell I'm paying to ship it. I could just throw it away.


Must be over $100 to ship this thing.

Take it off my hands, it's been sitting in the garage for years. Taking up space...

See previous posts for pics of build. It's MISSING the piston, which you will have to lathe yourself. Pretty easy just use some 2" HDPE stock.
4" PVC, 7' air tank.
All sch40 or sch80 build. No DWV in sight ...

I brought this up like 2 years ago, if I remember correctly...they all weigh a b|tch :wink:

But if you do some weight cutting down, i'm sure you could get them to work without blowing out the back of your housing.

Are you sure??? Some of them felt about the same weight as my cellphone, and that ...

Gaderelguitarist wrote:What is Academy? Some internet store?

All in all though a great find for anyone looking to create a large bore piston valve.

Just a sports store. http://www.academy.com/


I'm sure you can find these at any boating supply shop. I just need to bring some calipers next time I go.

I was there today and I was walking through the boating section and I saw these: Bow rollers


They come in all shapes/sizes/weights/material, ranging from soft rubber to hard plastic, to super light weight. I believe they ranged from 2-4", and were about $3-5 each.

http://img.alibaba.com/photo ...

For a project like a piston valve, having super accurate calipers doesn't matter. You're simply comparing one measurement to another, as long as it gives you the same reading every time, that's all you need.


But Mitutoyo is a very good brand. That's all my boss uses, and he's had them for 5+ years ...

Indexable carbide is the most expensive form of tooling to buy, and to use. BUT, you don't need a grinder. A fine diamond file will suffice for "touching up" the cutting edge.

Indexable carbides will break and chip at any excuse. :x I won't recommend that you get them for now, you don't really ...

150PSI? That's a LOT of pressure. To be honest, I probably wouldn't go above maybe 80PSI with this piston. It might do fine, but it's too much work to have it break.

If you don't mind waiting, I suggest building a solid HDPE piston. It will handle very high pressure easily.

Hey I was wondering how deep did you make the o-ring grooves and what size o-rings. Thanks because I am going to use your how-to for the piston in my gun. I don't get why no one else commented on your how-to I think its great and a very good desighn.

Also sorry for the bump I think good how-to's ...

Give me $2 for shipping and i'll mail you a small piece of either 1" or 2" HDPE. I bought the wrong size, so I'm not using them.